Back to Volume
Paper: Production of Phyllosilicates and Sulfates on Mars Through Acidic Weathering: The Río Tínto Mars Analog Model
Volume: 420, Bioastronomy 2007: Molecules, Microbes and Extraterrestrial Life
Page: 129
Authors: Fernández-Remolar, D. C.; Prieto-Ballesteros, O.; Amils, R.; Gómez, F.; Friedlander, L.; Arvidson, R.; Morris, R. V.; Gómez, D.
Abstract: Understanding the paleoclimate of Mars and the nature and extent of the interaction of water with crustal materials is essential to evaluate if life emerged once on Mars. Using recent results obtained by orbiters and surface rovers we propose that mildly acidic aqueous conditions produced phyllosilicate minerals during the Noachian period on Mars related to a CO2-rich atmosphere and an active hydrosphere. Underground neutralization of these mild acidic meteoric solutions with crustal materials would produce subsurface carbonates inside the crust after. Moreover, hydrothermalism provides mineralization to favor subsurface sulfide orebodies, but also secondary geochemical processes would also favor its formation. After cessation of the internal magnetic dynamo, the CO2-rich atmosphere was eroded and decreased by interactions with the solar wind and the hydrologic cycle that induced a climatic change to dry conditions where hydrological processes had subsurface dominance. Under this thin atmospheric aridic conditions photochemistry played an essential role in generating oxidizing and acidifying compounds that after entering the Mars crust promoted carbonate dissolution and sulfide oxidation. As a consequence, acid-sulfate evaporite deposits were precipitated in areas where acidic subsurface solutions emerged. Analogous processes have been observed in the underground fluids that feed the Río Tínto Mars analog. Seasonal subsurface of sulfur continued by a rapid oxidation induced by rainwaters, which induces a strong acidification through proton releasing (FeS2 + 3·O2 + 2 H2O → 2·SO42- + Fe2+ + 4 H+). This stage is followed by a neutralization and reduction of the ferric and sulfate rich acidified waters, which favors the subsurface carbonate precipitation. In addition, phyllosillicate sedimentation under the strong acidic conditions of Río Tínto, supports preservation of same minerals under early Noachian mildly acidic conditions.
Back to Volume